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Optical waveform shaper

a waveform and optical technology, applied in optics, instruments, electromagnetic transmission, etc., can solve the problems of reducing the s/n ratio, the receiver cannot demodulate/decode the received signal correctly, and the s/n ratio cannot be improved sufficiently, so as to achieve constant output optical power, improve noise reduction characteristics, and remove noise

Inactive Publication Date: 2009-12-15
FUJITSU LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The solution significantly improves the S / N ratio even in high-noise conditions by maintaining constant output optical power, enabling effective noise reduction and signal regeneration across both emission and extinction levels.

Problems solved by technology

As a result, the S / N ratio is degraded, posing the potential problem that the receiver cannot demodulate / decode the received signal correctly.
However, they cannot improve the S / N ratio sufficiently when there is large amount of noise (for example, ASE (Amplified Spontaneous Emission)).
It is particularly difficult to improve the S / N ratio when there is large amount of noise on the marked level of the input signal.
However, even with a multistage configuration, when the noise level is high and the S / N ratio of the input signal is significantly reduced, the waveform shaping has little effect, and consequently the signal waveform may be, nevertheless, distorted.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

embodiment 1

[0179]The configuration of the optical waveform shaper is the first configuration shown in FIG. 3 or the second configuration shown in FIG. 8A. Specifically, the optical waveform shaper adopts the configuration in which the interferometers 10 and 20 are connected in series, and one of the interferometers has a positive transfer function and the other has a negative transfer function. Also, the following parameters are given.[0180]The γ value of the highly nonlinear optical fibers 12 and 22: 25.0 (1 / (W·km))[0181]The wavelength dispersion of the highly nonlinear optical fibers 12 and 22: −0.5 (ps / nm / km)[0182]The wavelength dispersion slope of the highly nonlinear optical fibers 12 and 22: 0.08 (ps / nm^2 / km)[0183]The γ value of the low nonlinearity optical fibers 13 and 23: 1.3 (1 / (W·km))[0184]The wavelength dispersion of the low nonlinearity optical fibers 13 and 23: −0.5 (ps / nm / km)[0185]The wavelength dispersion slope of the low nonlinearity optical fibers 13 and 23: 0.08 (ps / nm^2 / km)...

embodiment 1-1

[0186]Configuration: The first configuration of FIG. 3[0187]The fiber length in the interferometer 10: 1.0 km[0188]The fiber length in the interferometer 20: 1.0˜10.0 km[0189]Synthesized transfer function: see FIG. 24

[0190]In FIG. 24, a function A represents the transfer function when the fiber length in the interferometer 20 is 1 km. Although the function A seems to have the best characteristics, it has substantially the same transfer function as that of one interferometer (the interferometer 10 in this case). That is to say, it is shown that connecting the interferometer 20 in the subsequent stage does not improve the synthesized transfer function when the fiber length of the interferometer 10 is short.

[0191]Here, a favorable transfer function refers to a function, which meets the following requirements, as explained with reference to FIG. 7.[0192](1) The width of the flat space region FWs is not zero, but has a certain width. When this requirement is satisfied, “0” is obtained as...

embodiment 1-2

[0194]Configuration: The second configuration of FIG. 8A[0195]The fiber length in the interferometer 10: 2.0 km[0196]The fiber length in the interferometer 20: 1.0˜10.0 km[0197]Synthesized transfer function: see FIG. 25

[0198]In this embodiment, a favorable synthesized transfer function cannot be obtained no matter how long the fiber length of the interferometer 20 is. A wide flat mark region FWm will not be obtained.

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Abstract

The present invention is an optical waveform shaper that utilizes a plurality of interferometers. Each interferometer has one of two types of transfer functions. One type is a first transfer function characterized as having a positive second order derivative of the output optical power in respect to the input optical power. Another type is a second transfer function characterized as having a negative second order derivative of the output optical power in respect to the input optical power. The characteristics of both the first transfer function and the second transfer function are actualized when the input optical power is in the neighborhood of zero and the output optical power shows substantially periodic change with respect to the input optical power. At least one of the plurality of interferometers uses the second transfer function.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an optical waveform shaper shaping the waveform of optical signals without conversion into electrical signals.[0003]2. Description of the Related Art[0004]In recent years, structures or methods utilizing optical signals have been applied to fields such as communications, signal processing and measurement. Such optical technology seems to show promise of further advances in the future.[0005]In order to improve the S / N ratio of optical signals, it is necessary to reshape the waveform of the optical signal. In optical communication systems, for example, the optical signal transmitted by a transmitter is attenuated with the transmission. Therefore, the waveform of a signal arriving at a receiver is distorted compared with that of the signal transmitted by the transmitter. As a result, the S / N ratio is degraded, posing the potential problem that the receiver cannot demodulate / decode the recei...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G01B9/02G02F1/01G02F1/21G02F1/295G02F1/35G02F1/365G02F2/00
CPCG02F1/3501G02F1/3517H04B10/299G02F1/3519G02F2201/16G02F2203/26G02F2001/212G02F1/212
Inventor HIRONISHI, KAZUOHOSHIDA, TAKESHIONAKA, HIROSHI
Owner FUJITSU LTD